1. Field of the Invention
The present invention relates generally to in situ ponds. More specifically, the present invention relates to methods of dissolving (or dissoluting) salts and other soluble minerals in situ ponds and other areas of salts accumulation.
2. Description of the Related Art
The process of producing solar salt involves pumping or feeding seawater or lake water by gravity to ponds for solar evaporation. In the first evaporation, the seawater is concentrated until it reaches saturation. Saturation is the concentration beyond which any further evaporation would result in the crystallization of Salt. Close to the end of the concentration process, gypsum calcium sulfate dihydrate starts to precipitate (“gypsum”). The gypsum continues to precipitate until the gypsum concentration diminishes. At that concentration the NaCl saturated solution is transferred to crystallization ponds where salts crystallize out.
The NaCl, which contains gypsum cannot be marketed and therefore is left to accumulate in the ponds where it originally precipitated. When the ponds fill up, other ponds need to be added to serve that purpose.
The Dead Sea Works in Israel and the Arab Potash Company in Jordan are processing carnallite for potash production. The carnallite a hydrated double salt of magnesium chloride and potassium chloride and is obtained by evaporation of the Dead Sea waters. NaCl precipitate first before reaching the potassium salt carnallite saturation. The NaCl continues to crystallize with the carnallite for a short while, rendering the carnallite too contaminated for processing.
The contaminated carnallite is dredged and dissolved to maintain the ponds in operation. In Utah, the US Magnesium operation recovers magnesium metal from the Great Salt Lake waters. The waters are evaporated to reach the magnesium chloride concentration that is necessary for metal recovery. NaCl and other potassium salts precipitate and accumulate in the ponds.
Dykes need to be raised for holding the Salts. The attempts to bring about the dissolution of the accumulated salts by way of flooding the salt ponds with seawater, or lake water brings limited results. The water in contact with the salt surface reached saturation in the process of dissolution, became heavy, contained about 26 grams of NaCl and reached a specific gravity of 1.2 gram/cc.
That layer of saturated solution serves as a shield, not allowing the fresh seawater above it to reach the NaCl below. In effect the dissolution stops. Also, dust and sand in the seawater cover the NaCl layer and interfere with the dissolution.
The Lithium operation in Salar De Atacama in Chile, the last crystallization pond contains the double salt LiCl.MgCl2.6(H2O ). which needs to be harvested for the recovery of LiCl. Convective dissolution in situ, the pond would recover the LiCl and bring about the precipitation of bischofite, MgCl2.6(H2O).
It is therefore desirable to provide a convective dissolution system to recover the most soluble salt in the first step while the remainder less soluble salt in the second step.